树形数据，改为一级

this.$xeutils.toTreeArray

或者 

submitForm() {
    //this.permissionTabledata   树形数据
    console.log(this.permissionTabledata);
// 引用下方treeToList
    var oncearr = this.treeToList(this.permissionTabledata);
}
treeToList(datas) {
    var arr = [];
    formateData(datas, 0);
    function formateData (datas, level) {
        var level = level || 0;
        level++;
        for (var i in datas) {
            arr.push(datas[i]);
            if (datas[i].children) {
                formateData(datas[i].children, level);
            }
        }
    }
    function getStr (level) {
        var str = '';
        for (var i = 1; i < level; ++i) {
            str += '—';
        }
        return level == 1 ? '' : '|' + str;
    }
    return arr;
},